1. Field of the Invention
The present invention relates to a stator of an electric motor.
2. Description of the Related Art
In order to fix a winding wound around a stator core, and enhance a heat dissipating effect from the winding, the stator of an electric motor is commonly provided with a resin molding section in an inner circumferential portion. Further, in order to enhance a water-proof property or omit a process of painting of an outer surface of the motor, a resin molding portion may also be formed in an outer circumferential portion of the stator. The resin molding portion preferably formed in the outer circumferential portion of the stator is preferably as thin as possible, for the purpose of downsizing the motor and efficiently releasing heat from the stator core to the outside. However, if a thin resin molding portion is formed by means of injection molding, a passage of resin is necessarily narrow, and therefore, it may be impossible to achieve sufficiently high fluidity of resin. As a result, there may be local portions in which resin is unfilled.
JP-A-2012-115050, JP-B-3552266 and JP-B-5124219 disclose a configuration in which a resin molding portion is formed in the circumference of the stator. JP-A-2012-115050 discloses a stator of an electric motor which includes a frame integrally formed with a stator core, a winding and a pair of insulators for insulating the stator core and the winding by way of resin. In order to fill resin into a gap formed between the pair of insulators, a through-hole extending from an outer circumferential portion to an inner circumferential portion of the stator core is formed as a passage of resin. JP-B-3552266 discloses a configuration in which a resin frame is formed so as to be integrally formed with a stator core and a coil wound round the stator core. Further, JP-A-2012-115050 discloses a configuration a resin molding portion is formed so as to cover an circumference of an armature of an electric motor.
There is a need for a stator of an electric motor in which an outer circumferential portion of the stator can be filled with resin.